Nanosecond laser temperature-jump and rapid chemical dilution of chemical denaturants using a new ultrafast continuous flow method are being developed and applied to the problem of describing the earliest events in protein folding. The laser temperature jump will be used to initiate the folding of cold-denatured proteins. In the ultrafast flow method the time course of protein folding is monitored by the fluorescence of the lone tryptophan (W59) which decreases as the protein folds due to quenching by the heme. The decay of the fluorescence, as well as the tryptophan-heme distance calculated from the quantum yield, are highly non-exponential extending from tens of microseconds to seconds. These results are interpreted in terms of energy landscape theory as "downhill run" to the native conformation with an effective diffusion constant decreases as the protein becomes more compact. Using time-resolved absorption spectroscopy to monitor the kinetics of geminate rebinding and conformational changes in myoglobin we have shown that the solvent viscosity, rather than the low temperature, is primarily responsible for the trapping of conformational substrates. This is demonstrated by placing myoglobin in a glass at room temperature and observing inhomogeneous reaction kinetics. The high solvent viscosity dramatically slows the rate of crossing the energy barriers separating substrates, and also suppresses any change in the average protein conformation following ligand dissociation. A simple model explain stretched exponential conformational relaxation in proteins has been developed. The basic idea of the model is that non- exponential relaxation results from transitions among two groups of protein conformational substrates connected by transition states of a single energy. We have measured oxygen binding curves of single crystals of hemoglobin in which the iron in the alpha subunits has been replaced by the non-oxygen binding nickel(II). These results provide additional strong support for the basic idea of allosteric theory that hemoglobin in the T quaternary conformation binds oxygen non-cooperatively.